Ignition system for reliable starting and maintaining regeneration process of diesel particulate filter

ABSTRACT

Ignition system for reliable starting and maintaining regeneration process of Diesel particulate filer wherein the said ignition system is composed of a diesel particulate filter inside the exhaust pipe, fuel burner beside the exhaust pipe, ignition system for fuel burner, a tube for supplying the fuel, a tube for air intake, spark plug with a special arrangement of spark gap, battery as electric energy supply, an engine control unit and high voltage screened interconnection cable whereas the ignition system comprises spark plug ( 5 ) and glow plug ( 6 ) with the air gap ( 11 ) formed by central electrode ( 7 ) of spark plug ( 5 ) and glowing tip ( 8 ) of glow plug ( 6 ), grounded by fixing point ( 10 ), whereas spark is formed in mentioned spark gap ( 11 ).The ignition controller ( 1 ) consists of spark generator and glow plug controller, both placed in the same enclosure

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation application of Patent Cooperation Treaty Application No. PCT/SI2012/000014, entitled “IGNITION SYSTEM FOR RELIABLE STARTING AND MAINTAINING REGENERATION PROCESS OF DIESEL PARTICULATE FILTER”, to HIDRIA AET DRU{hacek over (Z)}BA ZA PROIZVODNJO V{hacek over (Z)}IGNIH SISTEMOV IN ELEKTRONIKE D. O. O., Slovenia, filed on Mar. 15, 2012, which claims priority to Slovenian Patent Application Serial No. P-201100084, filed on Mar. 15, 2011, and the specification and claims thereof are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable.

COPYRIGHT MATERIAL

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention (Technical Field):

The major disadvantage of diesel engines comparing to gasoline ones are very small carbon particles (so called soot) that are present in exhaust gases during diesel engine running. Such small carbon particles are harmful to the human beings and the nature.

Modern diesel engines are, amongst other measures for reducing pollution, equipped with Diesel Particulate Filter (hereinafter referred to as DPF) in the exhaust system that is capable to trap such small particles. However, when sensors reports too high pressure drop inside the exhaust pipe, DPF is congested with soot and needs to be cleaned up. A process called DPF regeneration is automatically initiated by engine control unit. This process is based on heating the DPF to several hundred degrees Celsius, the temperature, where trapped carbon particles burn away with result of cleaning the DPF.

Heat needed for DPF regeneration usually comes from additional combustion of fuel in the exhaust pipe in front of DPF. Amongst others, post fuel injection, exhaust pipe fuel injection and fuel vaporizer techniques are used to bring unburned fuel in the exhaust pipe where it self-ignites with presence of heat. Additional heat generated heats up the DPF and thus causes the regeneration.

In case of very large diesel engines abovementioned methods are unable to bring enough fuel/air mixture in the exhaust pipe or self-ignition of fuel is not reliable. Therefore additional fuel burner with more than 50 kilowatts of heating power is installed beside the exhaust tube in front of DPF. Heat generated by fuel burning increases the temperature inside large DPF and causes its regeneration.

For reliable ignition of above mentioned fuel burner a powerful spark is needed. To prevent the possibility of explosion of unburned fuel in the exhaust system continuous sparking during DPF regeneration process is mandatory. As the fuel burner is located beside the exhaust tube, it is susceptible to soot deposition on the spark plug or ground electrode. Excessive soot deposition in an area where spark should occur could lead to spark fading or even to fuel burner ignition failure.

Preventing abovementioned malfunction is compulsory and is usually done with increasing of the spark energy. Spark arc voltage is constant at specified air gap and given operating conditions; hence the only way to increase the spark power is to increase the RMS current of the spark.

Tests have shown that RMS current values over 100 mA gives adequate results. At mentioned spark current levels the temperature of spark plug central electrode exceeds 800° C. and is high enough to burn eventual soot deposition. Beside mentioned effect also soot burning due to spark itself takes place.

The drawback of mentioned method of igniting of the fuel burner is electric shock hazard. It is commonly known fact that high currents flowing through human body could be lethal. In aforementioned fuel burner the current level >>100 mA RMS is needed to produce powerful spark, resistant to sooting. On the other hand, allowable current level is 60 mA RMS.

Additional measures as screening, warning labels application, covers with interlock loop or other actions are needed to make system safe enough.

The problem which has not been satisfactorily solved yet is that the ignition system for aforementioned fuel burner is not intrinsically safe, i.e., in case of intentional or not intentional removal of provided protections the human can receive lethal shock. Later is even more possible for service and garage employees that daily check and replace defective parts on engines.

The DPF regeneration system for heavy duty diesel engines is composed of a diesel particulate filter inside the exhaust pipe, fuel burner beside the exhaust pipe, ignition system for fuel burner, a tube for supplying the fuel, a tube for air intake, spark plug with a special arrangement of spark gap, battery as electric energy supply, an engine control unit and high voltage screened interconnection cable.

It is a purpose of this system to enable or facilitate the regeneration process of a DPF thus providing its long term reliable operation and reducing the presence of small carbon particles at exhaust system output.

It is an object of this system to flame heat the DPF to raise its temperature. When the system is switched on, first the spark is activated for a few seconds to heat up the central spark plug electrode and then the fuel/air mixture is sprayed in the spark region. Once the fuel comes into contact with spark it ignites and powerful flame is produced, which directly heats the DPF.

Software in the engine control unit supervises the operation of the DPF regeneration system. The software determines when the regeneration process takes place and how long it lasts. The software makes its decisions based on the signals it receives from the sensors in the engine and exhaust system.

During engine operation soot coming from not-ideal diesel combustion deposit mainly inside the DPF, a small portion of them set down also in the region where spark plug is located. Under extreme sooting condition the layer of soot at the spark gap could be so thick that prevents normal operation of the spark plug and thus impair the regeneration system or even cause it unusable.

One possible preventive measure could be continuous sparking without fuel/air mixture injection while engine running and consequently soot removing. Experiments have shown that mentioned solution is prone to fouling due to heavy sooting, but is not favorable as spark is degrading the central electrode of the spark plug all the time the engine is running.

Second option is usage of very powerful spark with ISPARK >>100 mA RMS that is capable of burning also thicker soot layer on the central electrode of the spark plug. Such spark is generated only during DPF regeneration process; its negative side is dangerousness or even fatality for human beings in case of direct contact with live parts.

It is an object and purpose of the present invention to provide powerful, reliable and intrinsically safe ignition system for fuel burner, particularly designed to combat harshest sooting situations and is at the same time not dangerous to humans.

In accordance with the invention, the object is achieved with special self-heating ground electrode that together with spark plug central electrode forms the spark gap.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to the ignition system for reliable starting and maintaining regeneration process of Diesel Particulate Filter, i.e. to an electrical arrangement of Ignition Controller and special mechanical arrangement of a spark gap located inside the combustion chamber of a Diesel Particulate Filter (DPF) regeneration system, ensuring a fast, intrinsically safe and reliable operation, predominantly used in heavy duty diesel engines for DPF regeneration.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention shall hereinafter be described according to an embodiment thereof and a drawing, representing:

FIG. 1 is a schematic diagram of the spark gap arrangement of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention covers generation of moderate power spark during DPF regeneration process with ISPARK <60 mA RMS that is not fatal for human beings with conjunction of special self-heated ground electrode. A standard glow plug is used as self-heated ground electrode.

The essence of the invention is a DPF regeneration system with fuel burner located beside the exhaust system, where ignition of mentioned fuel burner is done with spark, while the ground electrode is conventional diesel glow plug instead of plain piece of metal, connected to chassis ground. The main advantage of proposed system is that glow plug with its heat burns all soot deposition in the vicinity and thus cleans the spark gap. When the spark is generated, it occurs in the air gap between spark plug central electrode and glowing glow plug.

Mentioned spark gap arrangement provides anti-fouling capability and very reliable fuel burner ignition ability along with intrinsically safe spark current levels.

According to the invention, the ignition system for fuel burner intended for regeneration of DPF in heavy duty diesel engines is characterized in that the said spark gap 11 is formed with two main parts, spark plug 5 central electrode marked as positive electrode 7 and glowing tip 8 of conventional glow plug 6 marked as negative electrode. Spark 9 is formed in mentioned spark gap 11. Negative electrode is prolonged by glow plug metal body and is connected to ground at fixing point 10 to the fuel burner head 12. Burner head 12 is electrically connected with battery 2 negative terminal. Battery 2 supplies power to ignition controller 1 that generates spark voltage, led via high voltage cable 3 to spark plug 5. Ignition controller 1 supplies also current to the glow plug 6 via interconnecting cable 4. Such arrangement offers very good resistance against sooting and is at the same time intrinsically safe as spark current could be kept below 60 mA RMS. 

What is claimed is:
 1. An ignition system for reliable starting and maintaining regeneration process of a diesel particulate filter inside an exhaust pipe, said ignition system comprising: a spark plug and a glow plug proximate the exhaust pipe and forming an air gap between a central electrode of said spark plug and a glowing tip of said glow plug; and a fixing point acting as ground; and wherein a spark is formed in said air gap.
 2. The ignition system of claim 1, additionally comprising an ignition controller comprising a spark generator and a glow plug controller.
 3. The ignition system of claim 2 wherein both said spark generator and said glow plug controller are placed in the same enclosure.
 4. The ignition system of claim 2, wherein said ignition controller consists of a spark generator and a glow plug controller.
 5. The ignition system of claim 1, wherein spark current is below 60 mA RMS.
 6. A method of reliably starting and maintaining regeneration process of a diesel particulate filter inside an exhaust pipe, the method comprising: placing a spark plug and a glow plug proximate the exhaust pipe and forming an air gap between a central electrode of the spark plug and a glowing tip of the glow plug; and placing a fixing point acting as ground; and forming a spark in the air gap.
 7. The method of claim 6, additionally comprising controlling the spark via an ignition controller comprising a spark generator and a glow plug controller.
 8. The method of claim 7 wherein both the spark generator and the glow plug controller are placed in the same enclosure.
 9. The method of claim 7, wherein the ignition controller consists of a spark generator and a glow plug controller.
 10. The method of claim 6, wherein spark current is below 60 mA RMS. 